Multiple off-by-one errors in the (1) MakeBigReq and (2) SetReqLen macros in include/X11/Xlibint.h in X11R6.x and libX11 before 1.6.0 allow remote attackers to have unspecified impact via a crafted request, which triggers a buffer overflow.

The (1) GetDatabase and (2) _XimParseStringFile functions in X.org libX11 1.5.99.901 (1.6 RC1) and earlier do not restrict the recursion depth when processing directives to include files, which allows X servers to cause a denial of service (stack consumption) via a crafted file.

Multiple buffer overflows in X.org libX11 1.5.99.901 (1.6 RC1) and earlier allow X servers to cause a denial of service (crash) and possibly execute arbitrary code via crafted length or index values to the (1) XAllocColorCells, (2) _XkbReadGetDeviceInfoReply, (3) _XkbReadGeomShapes, (4) _XkbReadGetGeometryReply, (5) _XkbReadKeySyms, (6) _XkbReadKeyActions, (7) _XkbReadKeyBehaviors, (8) _XkbReadModifierMap, (9) _XkbReadExplicitComponents, (10) _XkbReadVirtualModMap, (11) _XkbReadGetNamesReply, (12) _XkbReadGetMapReply, (13) _XimXGetReadData, (14) XListFonts, (15) XListExtensions, and (16) XGetFontPath functions.

Multiple integer overflows in X.org libX11 1.5.99.901 (1.6 RC1) and earlier allow X servers to trigger allocation of insufficient memory and a buffer overflow via vectors related to the (1) XQueryFont, (2) _XF86BigfontQueryFont, (3) XListFontsWithInfo, (4) XGetMotionEvents, (5) XListHosts, (6) XGetModifierMapping, (7) XGetPointerMapping, (8) XGetKeyboardMapping, (9) XGetWindowProperty, (10) XGetImage, (11) LoadColornameDB, (12) XrmGetFileDatabase, (13) _XimParseStringFile, or (14) TransFileName functions.